ELMOR motor Germany ELMOR model ELMOR price

ELMOR motors consist of the motor body and the driver, representing a typical mechatronic product. Brushless motors refer to motors without brushes and commutators (or slip rings), also known as commutator-less motors. As early as the nineteenth century, when motors were first invented, the practical motors produced were of the brushless type, namely AC squirrel-cage asynchronous motors, which were widely used. However, asynchronous motors have many insurmountable drawbacks, resulting in slow development of motor technology. Transistors were invented in the mid-twentieth century, leading to the emergence of DC brushless motors that use transistor commutation circuits to replace brushes and commutators. This new type of brushless motor is called an electronically commutated DC motor, which overcomes the drawbacks of the first generation of brushless motors.

ELMOR motor starting

The resistance and inductance of the motor armature circuit are both small, while the rotating body has a certain mechanical inertia. Therefore, when the motor is connected to the power supply, the armature speed and the corresponding back EMF are very small at the beginning of the start-up phase, resulting in a large starting current. The maximum can reach 15 to 20 times the rated current. This current will cause disturbances to the power grid, mechanical shocks to the unit, and sparking at the commutator. Therefore, direct-on-line starting is only suitable for motors with a power not greater than 4 kilowatts (starting current is 6 to 8 times the rated current). To limit the starting current, a specially designed variable resistor is often connected in series in the armature circuit; its principle wiring is shown in Figure 1. During the starting process, as the speed continues to rise, each section of the resistor is short-circuited step by step in time, keeping the starting current within a certain allowable value. This starting method is called series resistance starting. It is very simple, the equipment is lightweight, and it is widely used in various small and medium-sized DC motors. However, due to high energy consumption during the starting process, it is not suitable for motors that start frequently or for medium and large DC motors. But for certain special needs, such as urban trams which start frequently, in order to simplify equipment, reduce weight, and facilitate operation and maintenance, the series resistance starting method is usually adopted. For DC motors with larger capacity, reduced voltage starting is usually adopted. That is, a separate adjustable DC power supply supplies power to the motor armature. Controlling the power supply voltage allows smooth motor starting and speed regulation. This method requires more complex power supply equipment.

ELMOR motor structure

The motor consists of stator magnetic poles, rotor, brushes, housing, etc. The stator magnetic poles use permanent magnets (permanent steel), including materials such as ferrite, AlNiCo, and NdFeB. According to their structural form, they can be divided into cylindrical and tile types, among others. The rotor is generally made of laminated silicon steel sheets, with enameled wire wound between two slots of the rotor core (three slots mean three windings), and each joint is soldered to the metal segments of the commutator. Brushes are conductive components connecting the power supply to the rotor windings, possessing both conductivity and wear resistance. Permanent magnet motors use single-metal strips, metal graphite brushes, or electrographite brushes. 2. Brushless DC motor: Consists of a permanent magnet rotor, multi-pole winding stator, position sensors, etc. The characteristic of brushless DC motors is the absence of brushes; they use semiconductor switching devices (such as Hall elements) to achieve electronic commutation, i.e., replacing traditional contact commutators and brushes with electronic switching devices. It has advantages such as high reliability, no commutation sparks, and low mechanical noise. Position sensors commutate the current in the stator windings in a certain order according to changes in rotor position (i.e., detecting the position of the rotor magnetic poles relative to the stator windings, generating position sensor signals at determined positions, which are processed by signal conversion circuits to control the power switch circuit, switching the winding current according to a certain logical relationship). There are three types of position sensors: magnetic, photoelectric, and electromagnetic. For brushless DC motors using magnetic position sensors, the magnetic sensing devices (such as Hall elements, magnetic diodes, magnetic transistors, magnetic resistors, or dedicated integrated circuits) are mounted on the stator assembly to detect changes in the magnetic field generated by the rotation of the permanent magnet rotor. Hall elements are mostly used in electric vehicles. For brushless DC motors using photoelectric position sensors, photoelectric sensing devices are configured at certain positions on the stator assembly, and a light shield is installed on the rotor, with the light source being an LED or a small bulb. When the rotor rotates, due to the action of the light shield, the photosensitive components on the stator will intermittently generate pulse signals at a certain frequency. For brushless DC motors using electromagnetic position sensors, electromagnetic sensor components (such as coupling transformers, proximity switches, LC resonant circuits, etc.) are installed on the stator assembly. When the position of the permanent magnet rotor changes, the electromagnetic effect causes the electromagnetic sensor to generate a high-frequency modulated signal (its amplitude varies with the rotor position). The operating voltage of the stator windings is provided by an electronic switch circuit controlled by the output of the position sensor.

ELMOR motor structure

Motor control structure: The DC brushless motor is a type of synchronous motor, meaning that the rotor speed is influenced by the speed of the stator's rotating magnetic field and the number of rotor poles (P), N = 120 · f / P. With a fixed number of rotor poles, changing the frequency of the stator's rotating magnetic field changes the rotor speed. A DC brushless motor adds electronic control (driver) to a synchronous motor, controlling the frequency of the stator's rotating magnetic field and feeding back the rotor speed to the control center for repeated correction, aiming to achieve characteristics close to those of a DC motor. That is, a DC brushless motor can maintain a certain rotor speed within the rated load range even when the load changes. The DC brushless driver includes a power section and a control section: the power section provides three-phase power to the motor, and the control section converts the input power frequency as required. The power section can accept direct DC input (generally 24V) or AC input (110V/220 V). If the input is AC, it must first be converted to DC by a converter (converter). Whether the input is DC or AC, before entering the motor coils, the DC voltage must be converted by an inverter (inverter) into 3-phase voltage to drive the motor. The inverter (inverter) generally consists of 6 power transistors (Q1 ~ Q6) connected to the motor as switches to control the current flowing through the motor coils, divided into upper arms (Q1, Q3, Q5) and lower arms (Q2, Q4, Q6). The control section provides PWM (Pulse Width Modulation) to determine the switching frequency of the power transistors and the commutation timing of the inverter (inverter). DC brushless motors are generally desired for speed control applications where the speed remains stable at the set value with minimal variation when the load changes. Therefore, the motor is equipped with Hall sensors (hall-sensor) inside to sense the magnetic field, serving as closed-loop speed control and also as the basis for phase sequence control. However, this is used only for speed control and cannot be used for position control.

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